What is an LH Surge?

There are three phases of your menstrual cycle: follicular phase, ovulatory phase, and luteal phase. In terms of the luteinizing hormone (LH) surge, the ovulatory phase is most important.

Increase in LH Followed By Surge

As the cycle comes closer to ovulation, LH levels start to rise. FSH, or follicle stimulating hormone, causes the egg to quickly mature in preparation for the ovulatory phase when the egg is released from the ovary. The luteinizing hormone causes a gradual increase in estrogen. As you move from the follicular phase to the ovulatory phase, LH rebuilds the lining of the uterus. The uterine lining thickens and fills with blood and nutrients in preparation for egg implantation. This process occurs every month until an egg is implanted in the uterine lining or your period begins.

Increased estrogen thins cervical mucus to help sperm travel toward the egg. Estrogen levels continue to gradually rise until they hit the tipping point that triggers LH surge. LH surge is a drastic increase in estrogen that forces the follicle to release the mature egg. When the egg releases into the fallopian tube it is known as ovulation.

Testing for Luteinizing Hormone Surge

There are currently over-the-counter urine tests called OPKs or ovulation predictor kits that measure the surge in urine. According to test manufacturers, the OPK test results are 99-percent accurate. There are two forms of over-the-counter LH surge testing kits, commonly marketed as ovulation tests. The first measures LH in urine for seven days. Women need to calculate the correct seven days to use the kit based on menstrual cycle and cervical mucus changes. Many women choose to use the calendar method to track ovulation cycles and choose the best time to perform LH surge home testing.

The other option is a monthly testing kit that includes enough tests to measure LH for 20 consecutive days. Testing often begins one to three days after the menstrual cycle ends depending on the length of your menstrual cycle. If your menstrual cycle lasts less than 35 days, you start testing on the day after your menstrual cycle ends. If your cycle lasts more than 35 days, wait two to three days before you start testing for LH surge.

When LH Surge Does Not Happen

LH Surge does not occur in all women, but when LH does not surge there is often an underlying condition causing lower than normal LH levels. Some of the conditions that can contribute to lower than normal hormone levels include Kallmann syndrome, hypothalamic suppression, and eating disorders.

Alternatively, having higher than normal LH levels can also cause problems with LH surge and fertility. Common conditions that cause an abnormally high LH level include premature menopause, Swyer syndrome and polycystic ovary syndrome.